New insights are needed in order for parents and practitioners to deal more effectively with juvenile disruptive behavior, delinquency, substance use, their comorbid conditions, and long-term sequelae. Longitudinal studies are one of the best tools to generate new knowledge about these vexing problems. The Pittsburgh Youth Study (N = 1,517) is now in its sixth year with data collected from target boys, their parent, and their teachers, and has achieved a high cooperation rate. This proposal aims at building a data base relevant for optimizing future preventive interventions. For that purpose the study proposes the continued follow-up of 506 subjects for another two data waves, spread over four years. The first aim is to examine the developmental course and prevalence of disruptive and antisocial behavior from ages 7 to 20, including the documentation of the sequence of onsets of problem behaviors (and the late onset of such behaviors), to trace developmental progressions in disruptive behavior, to examine long-term sequelae, and to identify developmental sequences leading to cessation of disruptive behavior. The second aim is to study the influence of comorbid conditions (attention-deficit/hyperactivity, anxiety, depression, substance use, and learning problems) on the course and outcome of juvenile disruptive behavior. The third aim addresses risk and protective factors relevant for the etiology of disruptive behavior, and examines the degree of specificity of such factors for different disorders and comorbid conditions. Finally, the study aims at elucidating subjects' and caretakers' help-seeking for mental health and other problems. The study measures a variety of risk and potential protective factors, the stability and change of these factors as they are likely to affect the development of different manifestations of disruptive behavior over time. Analytic aims are to narrow down those risk factors which can best explain different developmental processes, such as initiation, escalation, and desistance, and which can best account for individual differences in subjects' travelling on different pathways toward antisocial behavior. Analyses will make extensive use of data collected over the past five year and, together with the new data, will form the basis of analytic strategies geared at generating new knowledge to optimize future interventions, such as the identification of developmental pathways, the timing of risk factors, the interaction between these factors, and the identification of protective factors potentially amenable for prevention.